cement admixture

Abstract

The objective is to provide a cement admixture that can be constructed in the same way as ordinary concrete, and that exhibits good initial strength development without compromising the fresh properties, especially when using blended cements such as blast furnace cement. [Solution] The following components (A) to (C): (A) Quicklime 10~50% by mass (B) Gypsum 1~20% by mass (C) Rapid-hardening Portland cement with particle size of 50 μm or less, 40-80% by mass It contains, A cement admixture in which the mass ratio ((A+B) / C) of the total amount of component (A) and component (B) to the amount of component (C) is between 0.25 and 1.5.

Description

Technical Field

[0001] The present invention relates to cement admixtures and mortar or concrete.

Background Art

[0002] In recent years, from the viewpoint of reducing carbon dioxide emissions, etc., blended cements such as blast furnace cement and fly ash cement have been attracting attention as alternatives to Portland cement. Among these, blast furnace cement is a cement obtained by mixing fine powder of blast furnace slag, which is a by-product of an ironworks, and Portland cement. By mixing the fine powder of blast furnace slag, the amount of Portland cement used can be reduced, and the carbon dioxide emissions can also be reduced. As the cement using fine powder of blast furnace slag, it is standardized as blast furnace cement in JIS R 5201. However, there is a problem that the hydration reaction of blast furnace cement is slower than that of ordinary Portland cement, and the initial strength development property is low.

[0003] On the other hand, concrete using a quick-setting admixture containing calcium aluminate is known (for example, Patent Document 1, etc.). However, it is known that the addition of such a quick-setting admixture impairs the fluidity of fresh concrete. In order to ensure the fluidity of concrete, a retarder such as citric acid is added, but the time for ensuring the fluidity is at most about 1 hour at the limit, and if it is added excessively, there is a risk of causing poor hardening. And for the addition of the retarder, an adding device at the placing site is required, and it is necessary to adjust the addition amount of the retarder depending on the temperature conditions and the placing time, so more complicated management is required compared to the placing of general concrete.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The object of the present invention is to provide a cement admixture that can be constructed in the same way as ordinary concrete, and that exhibits good initial strength development without impairing the fresh properties, especially when using blended cements such as blast furnace cement. [Means for solving the problem]

[0006] Therefore, the inventors conducted various studies to solve the above problems and discovered that by adding fast-strength Portland cement with small particle size in a certain ratio to quicklime and gypsum, a cement admixture with good initial strength development can be obtained without impairing the fresh properties, even when using mixed cements such as blast furnace cement, thus completing the present invention.

[0007] In other words, the present invention provides the following [1] to [7]. [1] The following components (A) to (C): (A) Quicklime 10~50% by mass, (B) Gypsum 1-20% by mass, and (C) Rapid-hardening Portland cement with particle size of 50 μm or less, 40-80% by mass It contains, A cement admixture in which the mass ratio ((A+B) / C) of the total amount of component (A) and component (B) to the amount of component (C) is between 0.25 and 1.5. [2] Furthermore, the cement admixture described in [1] contains (D) calcium sulfamate. [3] The cement admixture according to [2], wherein the content of component (D) is 1 to 30% by mass in the cement admixture. [4] Mortar or concrete containing a mixed cement and a cement admixture described in any of [1] to [3]. [5] The mortar or concrete described in [4] further containing calcium sulfamate. A method for improving the initial strength development of mixed cement-containing mortar or concrete, characterized by adding a cement admixture described in any of [6][1] to [3]. [7] A method for producing mixed cement-containing mortar or concrete with improved initial strength development, characterized by adding the cement admixture described in any of [1] to [3] at any stage in the manufacturing process of mortar or concrete containing mixed cement. [Effects of the Invention]

[0008] By using the cement admixture of the present invention, the initial strength development of the resulting cement-containing mortar or concrete is significantly improved without impairing its fresh properties. [Modes for carrying out the invention]

[0009] Terms used herein shall be used in the sense commonly used in the art unless otherwise specified.

[0010] In the present invention, a cement admixture is a material that is mixed in addition to ordinary cement, aggregate, etc., when manufacturing mortar or concrete, and that affects the manufacturability of mortar or concrete and the properties of the resulting mortar or concrete. The cement admixture of the present invention has the characteristic of significantly improving the initial strength development of the resulting cement-containing mortar or concrete without impairing its fresh properties.

[0011] One aspect of the present invention is the following components (A) to (C): (A) Quicklime 10~50% by mass, (B) Gypsum 1-20% by mass, and (C) Rapid-hardening Portland cement with particle size of 50 μm or less, 40-80% by mass It contains, This is a cement admixture in which the mass ratio (A+B) / C, which is the total amount of component (A) and component (B) to the amount of component (C), is between 0.25 and 1.5. Another aspect of the present invention is a method for improving the initial strength development of a mixed cement-containing mortar or concrete, characterized by adding the aforementioned cement admixture. Another aspect of the present invention is a method for producing a mixed cement-containing mortar or concrete with improved initial strength development, characterized by adding the aforementioned cement admixture at any stage in the manufacturing process of the mortar or concrete containing mixed cement.

[0012] The quicklime (A) used in the present invention can be general industrial quicklime. Quicklime contributes to rapidly promoting the hydration of the mixed cement as a CaO source. The CaO content in the quicklime is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 93% by mass or more. Components other than CaO include small amounts of raw material components such as SiO2, Al2O3, Fe2O3, MgO, K2O, Na2O, MnO, TiO2, SO3, SrO, and CO2. Furthermore, the fineness of quicklime is measured in Blaine specific surface area of ​​3000-7000 cm². 2 A value of / g is preferred, and 4000-6000 cm 2 / g is preferable. The content of (C) quicklime in the cement admixture is preferably 10 to 50% by mass, more preferably 15 to 50% by mass, and even more preferably 20 to 45% by mass, from the viewpoint of daily strength development.

[0013] Examples of (B) gypsums used in the present invention include anhydrous gypsum, dihydrate gypsum, and hemihydrate gypsum. Anhydrous gypsum is particularly preferred from the viewpoint of strength development. In addition, both natural gypsum and chemically produced or by-product gypsums can be used. Examples of by-product chemical gypsums include flue gas desulfurization gypsum, phosphate gypsum, hydrofluoric acid gypsum, and titanium gypsum. The fineness of the gypsums is 3,000 to 12,000 cm² in Blaine specific surface area. 2 A value of / g is preferred, and the range is 4000 to 10000 cm. 2 / g is preferable. The content of (B) gypsum in the cement admixture is preferably 1 to 20% by mass, more preferably 2 to 19% by mass, and still more preferably 3 to 18% by mass from the viewpoint of 1-day strength development.

[0014] The (C) early-strength Portland cement used in the present invention is preferably an early-strength Portland cement having a particle size of 50 μm or less from the viewpoint of 1-day strength development, and more preferably an early-strength Portland cement having a particle size of 40 μm or less. The early-strength Portland cement having a particle size of 50 μm or less may be prepared by blending ordinary early-strength Portland cement so that the content as the early-strength Portland cement having a particle size of 50 μm or less becomes 40 to 80% by mass in the cement admixture, or may be prepared by previously producing and blending a classified product of early-strength Portland cement having a particle size of 50 μm or less, preferably 40 μm or less. For classification, various classifiers such as an air separator and a centrifuge can be used. By cutting the coarse particle portion of the early-strength Portland cement, a classified product having a particle size of 50 μm or less can be obtained. Here, the mineral composition of the early-strength Portland cement is a mineral composition calculated by the Bogue formula from the chemical composition, and the amount of 3CaO·SiO2 is preferably 55% by mass or more, more preferably 60% by mass or more, and still more preferably 63% by mass or more. The content of the (C) early-strength Portland cement having a particle size of 50 μm or less in the cement admixture is preferably 40 to 80% by mass, more preferably 40 to 78% by mass, and still more preferably 40 to 75% by mass from the viewpoint of 1-day strength development.

[0015] In the cement admixture of the present invention, from the viewpoint of obtaining excellent initial strength development without impairing the fresh properties, the mass ratio ((A + B) / C) of the total amount of components (A) and (B) to the content of component (C) is 0.25 to 1.5, preferably 0.3 to 1.2, more preferably 0.35 to 1.0, and particularly preferably 0.4 to 0.8. <00000​​The cement admixture of the present invention may further contain (D) calcium sulfamate. By containing calcium sulfamate, the early strength development property can be further improved. The content of calcium sulfamate in the cement admixture is preferably 1 to 30% by mass, more preferably 3 to 20% by mass. If it is less than 1% by mass, the effect of improving the strength development property is small, and if it exceeds 20% by mass, the workability may decrease. In addition, calcium sulfamate can be added separately from the cement admixture during the production of mortar or concrete. In that case, the addition amount is preferably 0.2 to 10% by mass, more preferably 1 to 5% by mass, based on the cement (excluding the early strength Portland cement in the cement admixture).

[0017] In addition to the above components, the cement admixture of the present invention may contain admixture materials generally used in mortar or concrete within a range that does not impair the effects of the present invention. Examples of such admixture materials include dispersants, waterproofing agents, pigments, water repellents, foaming agents, foaming agents, defoaming agents, retarders, shrinkage reducing agents, expanding agents, rapid hardening agents, heat of hydration inhibitors, thickeners, water retention agents, rust inhibitors, etc., and one or more of these can be added.

[0018] By using the cement admixture of the present invention, the early strength development property can be improved without affecting the workability of fresh mortar or fresh concrete.

[0019] As the cement used in the mortar or concrete of the present invention, various Portland cements such as ordinary, early strength, super early strength, low heat, and moderate heat, and blended cements can be used. In particular, the cement admixture of the present invention can be preferably used when using a blended cement such as blast furnace cement. Among them, blast furnace cement is preferred. Therefore, another aspect of the present invention is a method for improving the early strength development property of mortar or concrete containing a blended cement, characterized by adding the previous cement admixture. Another aspect of the present invention is a method for producing a mixed cement-containing mortar or concrete with improved initial strength development, characterized by adding the cement admixture of the present invention at any stage in the manufacturing process of the mortar or concrete containing mixed cement. The amount of the cement admixture of the present invention to be mixed in when manufacturing mortar or concrete is preferably 5 to 20 parts by mass, and more preferably 8 to 15 parts by mass, per 100 parts by mass of cement. [Examples]

[0020] The present invention will now be described in more detail with reference to examples, but the present invention is not limited in any way to these examples.

[0021] [Example 1] (Preparation of cement admixtures) A cement admixture was prepared by mixing the materials listed in Table 1 using a powder mixing device.

[0022] [Table 1]

[0023] (Evaluation test using mortar test specimens) To evaluate the performance of the cement admixtures (ADs), evaluation tests were conducted using mortar specimens. Mortar specimens were prepared by adding each prepared cement admixture under 20°C conditions. The materials used are shown in Table 2. The mortar mix is ​​shown in Table 3. After filling the mortar into a mold (dimensions: 4 × 4 × 16 cm), standard curing was performed. Workability and compressive strength were evaluated using these mortar specimens.

[0024] [Table 2]

[0025] [Table 3]

[0026] (Evaluation test) The evaluation test method is shown below. (1) Workability The workability after mixing was evaluated by its ability to fill molds. (2) Compressive strength The compressive strength at 1 day of age was measured by conducting tests in accordance with JIS R 5201 "Physical Testing Methods for Cement".

[0027] (Test results) The test results are shown in Table 4. Regarding workability, all levels demonstrated good filling properties into the formwork. Compared to the level without cement admixture (PL), all levels within the scope of the present invention showed good strength development.

[0028] [Table 4]

[0029] [Example 2] A cement admixture was prepared in the same manner as in Example 1, except that calcium sulfamate (SFC) was added in the amount shown in Table 5 to the cement admixture. Mortar test specimens were prepared using this cement admixture in the same manner as in Example 1, and workability and compressive strength (age 1 day) were evaluated. Workability was good, similar to Example 1. Compressive strength was good, as shown in Table 5.

[0030] [Table 5]

Claims

1. The following components (A) to (C): (A) Quicklime 10-50% by mass (B) Gypsum 1-20% by mass (C) Rapid-hardening Portland cement with particle size of 50 μm or less, 40-80% by mass It contains, A cement admixture in which the mass ratio ((A + B) / C) of the total amount of component (A) and component (B) to the amount of component (C) is between 0.25 and 1.

5.

2. Furthermore, the cement admixture according to claim 1, further comprising (D) calcium sulfamate.

3. The cement admixture according to claim 2, wherein the content of component (D) is 1 to 30% by mass in the cement admixture.

4. Mortar or concrete containing a mixed cement and a cement admixture according to any one of claims 1 to 3.

5. The mortar or concrete according to claim 4, further containing calcium sulfamate.

6. A method for improving the initial strength development of a mixed cement-containing mortar or concrete, characterized by adding a cement admixture according to any one of claims 1 to 3.

7. A method for producing a mixed cement-containing mortar or concrete with improved initial strength development, characterized by adding the cement admixture described in any one of claims 1 to 3 at any stage of the manufacturing process of the mortar or concrete containing mixed cement.

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